Conventional underwater tools are under water pneumatic tools, underwater hydraulic oil tools and underwater electrically-driven tools which respectively utilize air pressure, oil pressure and an electric power source for driving them. Such conventional underwater tools have certain disadvantages.
In the underwater pneumatic tools, the air is usually exhausted into the surrounding water so that the depth at which the underwater pneumatic tool can be used is limited due to backpressure on the discharged air. Moreover, large quantities of bubbles are generated so that visibility in the water is disturbed and in some cases, the use of acoustic communication through the water is disturbed.
In the underwater oil-hydraulic tools, two hoses must be connected between the hydraulic oil tool and a hydraulic oil supply to circulate the oil, so that the structure is complicated and the operation is troublesome, and moreover the water can be contaminated due to oil leakage resulting from damage to the hoses.
In underwater electrically-driven tools, electrical leakage into the water can occur so that it is dangerous for the diver to operate the underwater electrically-driven tool.
In order to eliminate such defects, an underwater hydraulic tool which uses a miniature and light weight hydraulic motor utilizing water under pressure as the power source has been devised, said hydraulic motor being rotated by introducing the water under pressure thereinto from a hose, said water under pressure being produced by sucking in water from a surrounding body of water by any suitable pump disposed on a working ship or the ground etc. and placing it under pressure, and discharging the pressurized water after rotating said hydraulic motor into the surrounding body of water.
When using such an underwater hydraulic tool having the miniature and light weight hydraulic motor, seizure of the rotating shaft of said hydraulic motor may occur due to overheating of rotating-sliding parts of said hydraulic motor.